View Full Version : MARS 2, JPL 0
That's the headline on today's edition of the local twice-weekly newspaper.
Understand that JPL is about three blocks from my house! < g >
Lots of unhappy rocket scientists around town today!
12-04-1999, 05:11 PM
There are still about 4 windows of opportunity where we might hear from it, under various scenarios of failure. The last of them ends about 5 days from now, but if we don't hear from it tonight the odds are pretty slim that it's ever going to talk to us.
The next window is around 8:30 PM tonight, Pacific time. If the lander went into 'safe' mode on landing (which would happen for lots of reasons), its first transmission would happen sometime between then and 10 PM. If we don't hear from it by then, it could be a failure of the dish antenna or the X-band transmitter. At that point, it'll try to communicate by relaying UHF messages through the Mars Global Surveyer. If the thing fell on its side because it landed on a rock, for instance, this is what would happen.
If we don't hear anything in that window (10:50 to 11:00 AM on Sunday), then it won't look very good. But there are still other possibilities. One is that one of the major systems failed. If that happens, the lander after six days without communication from Earth will have its 'command loss timer' kick in, and do a general reboot and start swapping in redundant components (almost all the critical systems have redundant backups).
If I were a betting man, I'd lay odds of 3-1 that the lander is lost. After tomorrow morning, I'd move those odds to maybe 20-1. After six days, if we haven't heard from it, make it 500-1.
But these spacecraft are pretty tricky, and NASA can try all kinds of schemes to 'wake up' a dead lander. I seem to recall that they managed to wake up one of the deep space probes that they thought was dead for several months. Its main mission was over, and they thought the batteries would be dead, and hadn't heard from it for a while, but they sent a bunch of commands to re-configure it for low-power use or something, and it came alive. So who knows?
12-04-1999, 05:25 PM
I live in Pasadena, Melin. The rocket scientists across the street haven't been home in three days. This year, it looks like we're not going to be the last house to put up Christmas lights for a change.
12-04-1999, 05:32 PM
Oh, and I forgot. Tell your paper to do better research. It's Mars 3, NASA 2. Of the last four missions, the Mars Climate Orbiter, and the original Mars Observer were lost, and maybe the polar lander. The Pathfinder and Global Surveyer were both highly successful.
This is not entirely unexpected, by the way. After the original Mars observer (a billion dollar program) was lost, NASA changed gears and started producing low-cost but high-risk vehicles under their 'Discovery' program. The idea was that if you can send five or six high risk missions instead of one low-risk missions, you increase the chances of getting at least some data back, since the overall risk is spread over multiple missions. The Polar Lander, Climate Orbiter, and Pathfinder combined were worth less than one major mission like Cassini. So taken as a whole, the project is a success even if the Polar Lander is lost. NASA's plan all along was to assume that at least some of these missions would be lost.
But I doubt the politicians will understand that. If they lose the polar lander, expect the politicians to start crying.
Hey, don't get me wrong, I'm a BIG fan of the space program in all its aspects. And JPL is fun to have so close -- there are lots of school-JPL interactions that are great for the kids, and they have a wonderful, if crowded, open house every year. Before it got so popular we used to be able to participate in up close and personal experiments with liquid nitrogen making things freeze solid.
And we got to see the little Rover thingie -- or a test version -- in its test field, made up to look like Mars. And we watched them build part of Cassini in a clean room, behind glass walls. Our signatures, digitalized, are on Cassini.
I hope we get a signal from the Polar Lander, but it won't change the fact that I'm a space program supporter. And no, none of my family works for the program.
And DAMN there's a lot of reporters in town!
Earl Snake-Hips Tucker
12-04-1999, 07:16 PM
Shouldn't we at least try to disable their defense systems before we try to land out scouting probes? :)
Ray Bradbury had a good story about a Martian invasion of earth gone haywire in "The Concrete Mixer."
12-05-1999, 10:13 AM
There does seem to be a "Mars Curse" on probes to the Red Planet. I (half)jokingly like to say that it's because the Martians need time to forge the fake data they'll feed the probes.
12-05-1999, 02:24 PM
Those martians are pretty tricky, because most of those failures happened on liftoff from the Earth, and not in Mars orbit.
12-06-1999, 11:13 AM
< Marvin The Martian >
Of course we are tricky! We're going to take over planet Earth!!
< /Marvin The Martian >
12-06-1999, 03:10 PM
Just getting to Mars is no mean trick. My father, a "rocket scientist" from the late 50s to the early 70s who worked on the Viking project, put it to me like this: "it's a lot easier to hit a scared deer at four hundred yards with a giant slingshot and a brick."
And Dad had the benefit of big ol', high thrust launchers that could horse a payload there on a "direct" path. Many of today's probes must rely on weaker launch vehicles and complicated gravity assists, along with the attendant heating and cooling that has potential to screw things up. I don't know if Polar took the scenic route or not.
Redundancy has been cut to the bone; in many cases, there are no backup systems to deal with a component failure. Reliability probably has not suffered with the "better, faster, cheaper" approach, but make no mistake: you get what you (don't) pay for. Problems that could potentially be solved from the ground suffer from the 40+ minute message send/receive/reply time imposed by the speed of light.
Furthermore, it should be noted that the successful Pathfinder mission was an "in-house" project produced entirely by the miracle workers at JPL. This one was largely out-sourced, cheaply. "Cheaply" may or may not include the use of summer interns to do that labor intensive work, such as inputting thousands of lines of navigation code... but that is irresponsible speculation on my part.
The exploration of Mars is still in its infancy. There is no standardized system for making landfall; the craft itself was landing in an area with conditions closely matched to the outside edge of the craft's performance range. It was expected to enter the atmosphere, pick a landing site with radar, and successfully place itself, correctly aligned, autonomously. That's a lot to ask for the price of a single Air Force fighter.
But hey, marginal odds, played consistently, can still yield a profit. I hope Congress remembers that it bought a higher probability of failure when it cut NASA's budget for the nth time. And I hope the next one works.
12-06-1999, 03:56 PM
Am I correct that this lander broadcasts to earth only at occassional intervals? I think that is a good way to cut power consumption, but wouldn't it be a good idea to have a constant feed during critical steps like landing? Even a little think like knowing the altitude when transmission stopped would offer a lot of clues as to what went wrong. The way it is now, they appear rather clueless.
12-06-1999, 10:29 PM
Keeves - you're right that it would be awfully nice to know when things went bad. However, transmitting during entry is easier said than done. For starters, much of the reentry the craft is enveloped in ionized plasma, which is problematic to transmit through. Then, the orientation of the craft and its antenna is constrained by reentry, meaning it can't point its antennas where needed. Also there's an aeroshell that has who knows what effect on the ability to transmit, and so on.
It's not impossible, but it does greatly complicate matters, and this was a small-budget mission. Also note that complexity adds risk. Even the shuttle is out of communication during part of its reentry, and that's right here on earth with no particularly tight alignment requirements on where to transmit _to_, on a great big craft we can load up with antennas and power sources out the ying-yang.
As for intermittent vs. continuous communication once a lander is down, that too is often constrained by the fact that the planet it's on is rotating, and so are we. Also the DSN is sometimes tasked to other things.
peas on earth
12-08-1999, 09:34 AM
same to you dhanson --
the Mars Polar Lander and Climate Orbiter weren't Discovery program missions. Check it out: http://discovery.nasa.gov/mission.html
12-08-1999, 03:18 PM
Apparently so. They were still built on the same philosophy (high risk, low budget). And actually, one of the press releases I read from a reputable organization (I *think it was the Planetary Society) described it as a Discovery mission.
But I stand corrected.
Go to: http://cnn.com/1999/TECH/space/12/08/mars.policy.ap/index.html The story quotes John Pike, space policy analyst for the Federation of American Scientists thusly: "I've always said about 'faster, better, cheaper': Two out of three ain't bad." And he goes on to say you can't pick which of those two you'll get.
Fighting my own ignorance since 1957.
Whoops! He says you can pick which two you want, but you can't have all three.
Fighting my own ignorance since 1957.
12-08-1999, 10:04 PM
I have a sign over my desk at work:
[list=1] On Time
Choose any two
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